1. Field of the Invention
The present invention relates generally to a photographic element and a method for the formation of color photographic images, and more particularly to a photographic element and a method for the formation of color photographic images wherein a novel yellow-forming coupler is used.
2. Description of the Prior Art
In the formation of colored images in color photography by a substractive color reproduction process, an aromatic primary amino compound, especially a N,N-disubstituted-para-diphenylene-diamino compound, is used as a developing agent, to reduce the silver halide grains in an exposed photographic emulsion, and the concurrently produced oxidation product of the developing agent is coupled with the coupler to form the image dye of the primary colors cyan, magenta or yellow.
The couplers for use in the above-described developing process have a phenolic hydroxyl group, an anilinic amino group or an active methylene group, and, by coupling with the oxidation product of the aromatic primary amino developing agent, form dyes which absorb light in the visible wave length range.
The yellow dye images show a specific absorption spectrum to a blue light in the wave length ranging from about 400 to 500 millimicrons. Previously known yellow-forming color couplers include .beta.-ketoacetoacetic esters, .beta.-diketones, N,N-malonic diamides and .alpha.-acylacetoamides, among which the .alpha.-acylacetoamides have been widely used to advantage in the field of color photography.
The .alpha.-acylacetoamides as couplers and the yellow dyes derived therefrom as images have, however, a number of disadvantages and are by no means completely satisfactory. For example, conversion of the .alpha.-acylacetoamides to the azomethine dyes requires 4 equivalents of silver halide as the oxidizing agent, per molecule, and, moreover, the maximum molecular extinction coefficient of the dyes formed is only on the order of about 20, 000 l. mol./cm. This means that an excessively large amount of silver halide is required to obtain the level of absorbance to blue light necessary in color photography. Furthermore, the incorporation of a large amount of silver halide into light-sensitive materials leads to some technical difficulties, such as an increase of light scattering in the emulsion and consequently, a decrease in the definition of the photographic images.
Furthermore, the .alpha.-acylacetoamides which give clear yellow dye images, generally have poor coupling reactivity with the oxidation product of the aromatic primary amino color developing agent so that a sufficient amount of dye does not result and this poor reactivity reduces the speed at which the developing process of the silver halide emulsion can be conducted, thereby making it difficult to carry out rapid development processing.
Moreover, the yellow dye images derived from the .alpha.-acylacetoamides lack sufficient resistance to light and humidity and thereby undergo deterioration in color when stored for a long period under severe conditions. This poor resistance of the yellow dye images consitutes one of the primary difficulties in storage of color photographs for long period.
In an attempt to eliminate the foregoing faults, a variety of inventions has been proposed.
For example, the specification of U.S. Pat. No. 3,265,506 discloses the derivatives of .alpha.-acylacetoanilide in which the carbonyl group of the acyl group is attached directly to the tertiary carbon atom of the alkyl group. It is true that dye images of derivatives of this class have both an excellent fastness and spectral absorption performance suitable for the color-reproduction by a substractive color photographic process, but a number of disadvantages concurrently accompany use of these derivatives. That is, these derivatives generally are poor in their oxidative coupling reactivity, and therefore, are unable to give yellow images having a high absorbance, and, the formation of the dyes is not completed in the color developing bath, so that the derivatives have to be subjected to a further processing containing a stronger oxidizing agent. Furthermore, in an attempt to make up for these faults, some derivatives were disclosed in which a hydrogen atom of the active methylene group is substituted by a halogen atom such as a fluorine or a chlorine atom, a sulfonyloxy group (see U.S. Pat. No. 3,415,652), or an acyloxy group (see U.S. Pat. No. 3,447,928). However, the replacement of a hydrogen atom in the active methylene group by such substituents is also accompanied by either of the following disadvantages. That is, coupling reactivity is not enhanced to a satisfactory extent, a marked color fog is produced, or the couplers, due to their own instability, gradually are changed into a condition in which they can no longer form a dye.
It is, therefore, an object of the present invention to provide a novel yellow-forming coupler suitable for use in color photography by a substractive color photographic process.
It is another object of the present invention to provide a method for the formation of dye images by effecting the development of a silver halide emulsion in the presence of a novel yellow-forming coupler.
It is another object of the present invention to provide color photographic light sensitive materials having a silver halide emulsion with a novel yellow-forming coupler incorporated therein.
It is another object of the present invention to provide a color developing composition containing a novel yellow-forming coupler.
It is yet another object of the present invention to provide a means for minimizing the amount of the silver halide contained in the photographic emulsion and improving the sharpness of the resulting images, with the use of a novel yellow-forming coupler.
It is another object of the present invention to provide a color photographic light-sensitive material suitable for rapid color development using a fix-bleaching bath containing both a weak oxidizing agent and a silver complex forming agent.
It is still another object of the present invention to provide yellow dye images having suitable spectral absorption characteristics for color reproduction by a substractive color photographic process, together with an excellent stability.
Other objects of the present invention will become apparent from the disclosure contained herein and the appended claims.